The present invention relates to a method for fabricating a semiconductor device and, more particularly, to a method of forming a fuse for a semiconductor device.
When a failure occurs in a semiconductor device, a fuse is used to repair such a failed part. In other words, in the case in which such a fail is neither a hard fail nor a severe fail after a semiconductor fabrication process is completed, a fuse line, that is a redundancy line, is cut off using a laser. Thereby, the operation of the semiconductor device is made possible.
Up to now, the fuse is not separately formed by an additional process, but is formed by using a conductive layer made up of a bit line, a word line, or the plate line (upper electrode) of a capacitor.
FIG. 1 is a cross-sectional view of a semiconductor device using an upper electrode as a fuse.
Referring to FIG. 1, a substrate 10 has a cell region and a fuse region. The cell region of substrate 10 is formed therein with cylindrical capacitors 14. Here, each cylindrical capacitor 14 is formed in the structure in which a lower electrode 11, a dielectric layer 12, and an upper electrode 13 are stacked. Particularly, the upper electrode 13 of the cylinder capacitor 14 is used as a fuse in the fuse region.
An insulation layer 15 is formed over the whole surface of the resultant structure, which includes the cylindrical capacitors 14. The insulation layer 15 of the fuse region is selectively etched, that is, is subjected to repair-etching until the insulation layer 15 remains over the upper electrode 13 used as the fuse at a predetermined thickness.
As described above, the typical method has used the upper electrode 13 as the fuse in the fuse region.
However, in the cylindrical capacitor 14 of the typical method, the upper electrode 13 is located slightly above the bit line without a great height difference, so that the insulation layer 15, which is formed over the fuse, becomes too thick. More specifically, the height of the upper electrode 13 used as the fuse in the fuse region is reduced by D1, compared to that of the upper electrode 13 that is originally formed over the uppermost layer of the capacitor, so that the insulation layer 15 has a thickness corresponding to the height difference.
For this reason, during the repair-etching, it takes excessive time to perform the repair-etching, and it is difficult to control the insulation layer 15 having a predetermined thickness so as to be formed over the fuse at a uniform thickness. Thus, a technique in which a metal interconnection formed above the capacitor is used as a fuse has been proposed.
FIG. 2 is a cross-sectional view of a semiconductor device using a metal interconnection as a fuse.
Referring to FIG. 2, a substrate 20 has a cell region and a fuse region. The cell region of the substrate 20 is formed therein with cylindrical capacitors 24, each of which is stacked by a lower electrode 21, a dielectric layer 22, and an upper electrode 23. A first insulation layer 25 is formed over the whole surface of the resulting structure, which includes the cylindrical capacitors 24.
A metal interconnection 26 is formed above the first insulation layer 25. The metal interconnection 26 is used as a metal interconnection in the cell region, but as a fuse in the fuse region. A second insulation layer 27 is formed over the metal interconnection 26. Then, the second insulation layer 27 of the fuse region is subjected to selective repair-etching, so that it remains on the metal interconnection 26 at a predetermined thickness.
As described above, in the case in which the metal interconnection is used as the fuse, the etching is not performed by thicknesses of the capacitor 24 and the second insulation layer 27, compared to the case in which the capacitor is used as the fuse, so that the repair-etching becomes easier.
However, in the case in which the metal interconnection is used as the fuse, the layers stacked from the bottom to the top are formed in a multi-layered structure. Thus, when laser fuse cutting is subsequently performed, points between the respective layers, reacting with laser power, are different from each other, so that it is difficult to cut the fuse. Further, after the laser fuse cutting, cracks occur in the first insulation layer 25 under the fuse on either side of the fuse, and thus an electrical short occurs between the neighboring fuses.
In the typical fuse failure, it can be found that, after the laser fuse cutting, oxide cracks occur under the fuse, which is not cut, on either side of the fuse, and seem as if aluminum (Al) is melted down. For this reason, the short occurs between the neighboring fuses, and thus the operation of the cell becomes impossible.